1. Technical Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a lamp and, more particularly, to an improvement in electrically welding to the base the outer end of an external lead-in wire drawn out of the gap between a bulb and a base of a lamp assembly.
2. Description of the Prior Art
There is a prevalent method conventionally used to connect the outer end of an external lead-in wire coming from a glass bulb which is an airtight vessel of a lamp assembly, e.g., an incandescent lamp assembly. The outer end of the wire is conductively connected to a metallic terminal or a base which, in turn, is coupled or fixed on an end of the glass bulb by means of an arc-welding.
In this conventional process, the lamp assembly is prepared by coupling to a base, a bulb having external lead wires connected to its filament. This is accomplished with a base coupling device. One of the external lead-in wires is drawn out its outer end between the bulb and the edge of the base. The lamp assembly is supported and conveyed by a support. A welding rod, to which negative DC voltage and high frequency voltage may be applied, is arranged to be adjacent to the outer end of the external lead-in wire at the welding stage.
Therefore, an arc discharge takes place between the welding rod and the outer end of the external lead-in wire, and then the outer end of the external lead-in wire is welded to the base.
As compared with a method and apparatus that will effect brazing of the external lead-in wire to the base with a metallic solder, the above-described method and apparatus is advantageous in that it keeps the base coupling device from being stained by a soldering liquid, keeps the base from being discolored by the soldering liquid, and further permits coupling of the aluminum base to the bulb and coupling of the base of brass to the bulb without changing equipment.
However, the prevailing, conventional method and apparatus requires that there be a gap between both electrodes, i.e., the welding rod and the outer end of the external lead-in wire, which gap must be maintained at an extremely short distance for generation of an arc discharge through the air for arc welding. Moreover, the external lead-in wire cannot be welded to the base by a desired arc current unless a high voltage is applied to generate the arc. Furthermore, a fluctuation in power voltage for arc welding and a fluctuation in gap due to a consumption of the welding rod which works as an electrode for the arc welding, inevitably induce a fluctuation in arc current, a disability to generate the arc, or an unsteadiness of arc welding. Therefore, an extremely fine adjustment on an arc generating device must be provided for steady arc welding.